The present invention concerns a low-stretch floor covering material applicable both as wall to wall (broadloom) carpets and as carpet tiles, said material exhibiting both a dimensional stability under climatic changes in accordance with the specifications for carpet tiles, especially for contract carpeting and the ability to be wound onto broadloom rollers. The invention further concerns a method of manufacturing a floor covering of the kind stated in the introduction and in which in an initial production step a web-formed semi-manufactured material is produced which comprises pile material being retained to a primary backing layer.
Low-stretch and dimensionally stable floor coverings include wall-to-wall (also often called broadloom) carpets and carpet tiles exhibiting a low degree of shrinkage and/or expansion lengthwise and/or widthwise, and consequently being highly capable of resisting varying moisture and heat impacts in use. Especially within the field of contract applications the dimensional stability of carpet tiles is to-day--due to their construction--considerably higher than that of broadloom carpets. To compensate for the lower dimensional stability of broadloom carpets they are for contract applications to-day glued down to sub-floors by means of a permanent glue. Carpet tiles are only installed and glued down by means of tackifier or are simply meant to be held in place by their high weight.
The known low-stretch and dimensionally stable floor coverings when used as wall-to-wall carpets comprise a semi-manufactured material with pile material which is retained to a primary backing layer having a secondary backing layer which e.g. may consist of a coating of natural rubber, chalk-filled (calciumcarbonate-filled) SBR-latex foam or polyurethane foam or the like. These backing layers are normally applied in a thickness of 2-8 mm. Because of their elastomeric properties foamed backing layers contribute significantly to the walking comfort. Additionally, the foamed backing layers also provide good temperature and sound insulation.
These known foamed backing layers, however, entail significant adverse environmental impacts, which are undesired in particular in the light of the present strict demands on environmentally friendly and re-usable products. By re-usable products are meant products containing components which can be melted down and again enter into a production process, or components which by incineration give approximately nul residual ash percentage. The foamed backing layers often give off residual gases for prolonged periods after production entailing risk of nuisance to the indoor climate in the room where the carpet has been laid out. At the same time it is a problem that the foamed backing layers after use for some length of time of the floor covering stick so well to the underlying floor that the foamed backing layer often in very large areas is separated from the floor covering when worn-out floor covering is to be removed. The large areas with attaching remains of foamed backing layers must then be removed in a time-consuming working operation before a new floor covering can be laid on the floor.
The most significant disadvantage of the known floor coverings with foamed backing layer, however, consists in the limited possibilities of disposing of the used carpet coverings and the related unfortunate environmental impacts. In case of e.g. foamed chalk-filled SBR-latex backing coatings on worn out wall-to-wall carpets it is in practice at disposal only possible to achieve the level "incineration without energy recovery". Chalk-filled foam backing layer contain a high concentration of inorganic materials which are left as ash after incineration.
The generally known carpet tiles are widely used in particular as so-called project carpeting, that is, carpet especially for contract areas and for industrial use. Understood herein by carpet tile is a regularly formed piece of carpet which (measured according to specifications formulated for this purpose by national inspection agencies such as for instance TNO) has a shape and dimension stability under climatic changes sufficient to form a continuous floor covering under all conditions. A representative standard used in many countries at the time the present invention was made is DIN 66095 Teil 2 according to which the extension under specified climatic changes must not exceed +0.2%, and the shrinkage must not exceed -0.4%. Test methods for extension and shrinkage are e.g. ISO 2551 and DIN 54318.
In such applications carpet tiles have great advantages compared with conventional broadloom carpets. The tiles are for instance easy to take up, whereby easy access can be obtained to the space under the floor for (re)positioning for instance computer and electricity cables. Carpet tiles can also be easily laid without unnecessary disruption of the normal activities in a room area. In addition, carpet tiles can be replaced locally in simple manner, which is advantageous when particular parts of a room area are used more intensively than others. They are also compact and therefore simple to transport, particularly in high-rise office buildings where rolls of carpet can cause great transport problems.
The known carpet tiles are usually provided with a relatively heavy secondary backing layer and binder layer in order to ensure their shape and dimension stability. The secondary backing layer is generally made of a strong coating of glass-reinforced bitumen or glass-reinforced PVC coating. The specific weight of a conventional carpet tile therefore amounts to roughly 5 kilograms per square meter.
A representative example of such carpet tiles is described in EP 0278690 A2. In order to provide a carpet tile with good dimensional stability, good lay flat characteristics, and which may be produced by an in-line production method, a carpet tile is suggested, which comprises a fibrous face wear surface secured to a primary backing sheet,
a first precoat layer on the primary backing surface and comprising a hotmelt bitumen or petroleum resin composition, PA1 a second precoat layer secured to the first coating layer and which second coating layer comprises a bitumen hotmelt composition, PA1 a third coat backing layer which comprises a bitumen hotmelt composition, and PA1 a secondary backing sheet material to provide dimensional stability to the carpet and secured to the third coating backing layer. Dimensional stability is achieved by the secondary backing comprising a woven or non-woven glass fibre scrim and by the high total weight of the tile. PA1 initially producing a web-formed semi-manufactured material comprising a pile material retained to a primary backing layer, PA1 heating a web-formed secondary backing layer having a specific weight of 70-1000 g/m.sup.2 and comprising a needled fibre structure of essentially non-moisture absorbing thermoplastic, polymer-containing, continuous or staple fibres to a temperature at least corresponding to the lowest softening temperature for the fibre materials in the fibre structure so as to provide an interfixation of the fibres, PA1 joining the back side of the web-formed semi-manufactured material with the web-formed backing layer by interleafing an adhesive layer preferably in an amount, so that the specific weight of the secondary backing and the adhesive does not exceed 1800 g/m.sup.2, said adhesive layer comprising an organic polymer-containing binder having a reaction temperature which is lower than the melting temperature for the majority of the fibre material content in the fibre structure and activating the binder by heat application, PA1 cooling the formed floor covering material so as to provide an essentially non-moisture absorbing bonded adhesive layer, PA1 winding the material onto broadloom rollers and optionally cutting the material wholly or partially into carpet tiles. PA1 that during extrusion on the semi-manufactured material they are sufficiently flowable to be able to penetrate into the primary backing forming part of the semi-manufactured material without soaking through pile to the top of the carpet. PA1 that sufficiently open-time is available--the hot-melt binder must stay liquid for sufficiently long so as to allow adhesion of the secondary backing thereto. PA1 A totally recyclable system with almost no residue. PA1 Reduced environmental costs. PA1 A product based on environmentally up-to date, non-toxic materials. PA1 Improved production stability and control of the product quality. PA1 Lower energy consumption and production costs. PA1 Much higher production speeds than conventional backing plants. More than 3-4 times the speed when manufacturing and backing carpets with light-weight secondary backings. PA1 Reduced physical space, since no drying ovens are needed. PA1 Possibility of exploiting advantages of large scale production and improved logistics.
In order to further improve the dimensional stability EP 0420661 A2 describes a carpet tile comprising a wear surface and a primary backing comprising a solid, hotmelt composition and a secondary backing composed of adjacent layers of a porous, glass fibre sheet material e.g. tissue, non-woven glass fibre and a porous, fibrous sheet material with a fibrous sheet material as the exterior surface of the secondary backing layer, and wherein the hotmelt composition has penetrated and saturated the glass fibre material but has only partially penetrated the fibrous sheet material sufficiently to bond the fibrous sheet material. Typically, the carpet tile comprises a fibrous carpet material wherein the primary backing is a bitumen or a bitumen modified hotmelt composition. The secondary backing comprises separate, adjacent layers of a porous, lightweight glass fibre tissue sheet material which in itself gives the carpet tile the improved dimensional stability. However, in EP 0420661 polypropylene, non-woven sheet material is characterized as not in itself being a satisfactory material as a secondary backing carrier sheet.
EP 0590189 A1 was filed on Dec. 30, 1992 and published on Apr. 6, 1994 (Art.54(3)EPC) for DE, FR, GB, and NL. It confirms the disadvantages of prior art carpet tiles comprising bitumen/asphalt backing members or PVC-backings.
According to one embodiment of this invention a tile-shaped carpet is provided which comprises a backing member and an upper layer formed on the backing member, both of which are made of a propylene resin. Preferably the upper layer includes a base fabric sublayer and a pile sublayer, both of which are made of propylene resin.
While reference is made to polypropylene fibres as part of the upper layer, the backing member is only described as being made of either propylene, monopolymer or copolymers of propylene and ethylene butene-1 and the like, which may comprise a regenerated product of the propylene resin. It is preferred to use an amorphous alpha-olefincoplymer and in fact the only embodiment specifically described is extrusion-moulded back-up members. The document comprises no reference to needled and textiled back-up members.
The known carpet tiles have a large number of drawbacks, however. The disposal and processing of the tiles at the end of their useful life thus causes great problems due to the nature and quantity of the materials used. When they are burned a significant portion, up to about 60% by weight, of the bitumen-containing tiles is left over in the form of ash.
Incineration of products such as tiles with PVC backing layers demands high energy supply during incineration, because PVC contains chlorine which uses energy during incineration instead of generating energy. Chlorine is also a toxic and etching gas which easily reacts with other inorganic and organic substances, wherefore incineration of floor coverings with PVC backing layer calls for special environmental measures during the incineration process.
It is moreover expected that the problems associated with the processing of waste tiles will become more pressing in the future since, with regard to the large numbers of carpet tiles laid and replaced annually (in Europe more than 40 million square meters with a weight of about 200,000 tons), legal requirements relating to the environmentally friendly processing thereof can be anticipated in the short term.
In addition, due to their comparatively heavy weight the known carpet tiles can only be simultaneously transported and laid in relatively small quantities. Moreover there is a considerable danger of back disorders for the carpet installers.
As previously mentioned the construction of carpet tiles and broadloom carpets is totally different. Therefore, carpet tiles and broadloom carpet have conventionally been produced by different processes and on different types of manufacturing equipment. This has been due to the mentioned different materials which the carpet industry has had to use until now for meeting the application requirements for these two different products. For manufacturing carpet tiles the relatively stiff, heavy weight backing of bitumen or PVC with glass have been used, or for broadloom carpets the backing has conventionally been relatively flexible, been consisting of calcium carbonate filled foam or equivalent materials. So far it was therefore not possible to integrate the manufacture of these two types of carpets in one and the same process.
From EP 0547533 A1 a stretchable floor covering is known which when being laid out are often stretched by many percent lengthwise and widthwise, whereafter the edges of the stretchable floor covering are secured to adjoining panels by means of nail lists or the like. The secondary backing layer is instead of the previously known foamed coatings constituted by a backing layer with a fibre structure being embedded in or encompassed by a textile bonding so as to impart acceptable strength properties to the secondary backing layer for use as a stretchable floor covering. By the textile bonding is meant that the fibre structure may e.g. be needlepunched to an underlying strength imparting web, or that the fibre structure is provided with stitches or loops in the longitudinal and cross-sectional directions, e.g. according to the known Maliwatt or Kettenwirk principles. The specification, however, provides no directions for a backing layer with a fibre structure being sufficiently dimensionally stable in the longitudinal and cross-sectional directions for enabling production of a low-stretch and dimensionally stable floor covering possessing the same strength and dimensional stability properties and walking comfort as the known floor coverings with foamed backing layers and the same dimensional stability as the known carpet tiles.